This invention is generally directed to layered photoresponsive imaging members, and more specifically to imaging members having incorporated therein as photogenerating substances, certain dihydroxymetal phthalocyanines, especially dihydroxygermanium phthalocyanines. In one embodiment, the present invention envisions a layered photoresponsive imaging member comprised of a dihydroxygermanium phthalocyanine photogenerating composition, in contact with a hole transport layer. These members are useful for generating images in electrostatic latent imaging systems, and more specifically the imaging members of the present invention are sensitive to wavelengths in the infrared region of the spectrum, that is for example, wavelengths of from 800 to 900 nanometers.
Numerous different xerographic photoconductive members are known including, for example, a homogeneous layer of a single material such as vitreous selenium, or a composite layered device, containing a dispersion of a photoconductive composition. An example of a composite xerographic photoconductive member is described in U.S. Pat. No. 3,121,006, wherein there is disclosed finely divided particles of a photoconductive inorganic compound dispersed in an electrically insulating organic resin binder. The binder materials disclosed in this patent comprise a material which is incapable of transporting for any significant distance injected charge carriers generated by the photoconductive particles. Accordingly, as a result, the photoconductive particles must be in a substantially contiguous particle-to-particle contact throughout the layer for the purpose of permitting charge dissipation required for a cyclic operation. Thus, with the uniform dispersion of photoconductive particles described, a relatively high volume concentration of photoconductor material, about 50 percent by volume, is usually necessary in order to obtain sufficient photoconductor particle-to-particle contact for rapid discharge. This high photoconductive loading can result in destroying the physical continuity of the resinous binder, thus significantly reducing the mechanical properties thereof. Illustrative examples of specific binder materials disclosed in the '006 patent include, for example, polycarbonate resins, polyester resins, and polyamide resins.
There are also known photoreceptor materials comprised of inorganic or organic materials wherein the charge carrier generating, and charge carrier transport functions, are accomplished by discrete contiguous layers. Additionally, layered photoreceptor materials are disclosed in the prior art which include an overcoating layer of an electrically insulating polymeric material. However, the art of xerography continues to advance and more stringent demands need to be met by the copying apparatus in order to increase performance standards, and to obtain higher quality images. Also, there is desired layered photoresponsive imaging members which are responsive to infrared illumination selected for laser printing systems.
Further, recently there has been disclosed other photoresponsive devices including those comprised of separate generating layers, and amine transport layers as described in U.S. Pat. No. 4,265,990, and overcoated photoresponsive materials containing a hole injecting layer, overcoated with a hole transport layer, followed by an overcoating of a photogenerating layer, and a top coating of an insulating organic resin, reference U.S. Pat. No. 4,251,612. Examples of photogenerating compositions disclosed in these patents include trigonal selenium and phthalocyanines. The disclosures of each of these patents, namely, U.S. Pat. Nos. 4,265,990 and 4,251,612 are totally incorporated herein by reference.
Furthermore, there is disclosed in U.S. Pat. Nos. 4,232,102 and 4,233,383, photoresponsive imaging members comprised of trigonal selenium doped with sodium carbonate, sodium selenite, and trigonal selenium doped with barium carbonate, and barium selenite or mixtures thereof.
There is also known layered photoresponsive imaging members sensitive to visible light and/or infrared radiation, reference for example U.S. Pat. No. 4,415,639, the disclosure of which is totally incorporated herein by reference. In this patent there is disclosed a layered photoresponsive imaging member comprised of a photogenerating layer, a photoconductive layer, and a hole transport layer. More specifically, there is illustrated in this patent an improved photoresponsive imaging member comprised of a supporting substrate, a hole blocking layer, an optional adhesive interface layer, an inorganic photogenerating layer, a photoconductive composition capable of enhancing or reducing the intrinsic properties of the photogenerating layer, and a hole transport layer. As photoconductive compositions for this device there can be selected various squaraine pigments, including hydroxy squaraine compositions. Moreover, there is disclosed in U.S. Pat. No. 3,824,099, certain photosensitive hydroxy squaraine compositions. According to the disclosing of this patent the squaraine compositions are photosensitive to normal electrostatographic imaging systems.
While the above-described photoresponsive imaging members are suitable for their intended purposes, there continues to be a need for improved members, particularly those which are sensitive to infrared radiation. Additionally, there is a need for imaging members having incorporated therein phthalocyanine compositions which are relatively nontoxic, and can be easily prepared and purified. Moreover, there continues to be a need for imaging members having incorporated therein photogenerating layers comprised of phthalocyanine compositions that can be prepared by simple processes. Also, there is a need for imaging members possessing desirable sensitivity, particularly in the wavelength region of from 800 to 900 nanometers, low dark decay characteristics, high charge acceptance values, and wherein these members can be selected for repeated cycling in a xerographic imaging apparatus. There also is a need for improved layered imaging members wherein the photogenerating pigment selected for one of the layers is substantially inert to users of an imaging apparatus with these members. Furthermore, there continues to be a need for improved infrared sensitive layered photoresponsive imaging members useful in a number of imaging and printing systems wherein lasers, such as gallium arsenide aluminum lasers, are selected.